1. Field of the Invention
The present invention relates to a charge control apparatus used in conjunction with a vehicle battery that supplies power to a drive motor mounted in a vehicle and electrical parts of the vehicle.
2. Description of the Related Art
There is a method for charging a car battery achieved by converting the regenerative energy manifesting when the vehicle is decelerating to regenerative power with a motor or the like and supplying the regenerative power to the battery to charge it in the related art.
The limit on the rate of power absorption by the battery per unit time varies depending upon the quantity of power already stored in the battery. FIG. 7 illustrates the relationship between the battery SOC (state of charge) and the rate of gas generation resulting from the electrolysis of the battery fluid manifesting when a charging current flows to a lead-acid battery normally used for a vehicle battery, which is ascertained through testing. A gas is generated as a result of the electrolysis of the battery fluid if the limit to which the battery is capable of absorbing the regenerative power is exceeded.
The power absorption limit of the lead-acid battery per unit time is high when the quantity of power having been stored in the battery is small, i.e., when the sulfuric acid concentration in the battery fluid is low. If, on the other hand, the quantity of power having been stored in the battery is large, i.e., if the sulfuric acid concentration in the battery fluid is high, the power absorption limit per unit time is low. Accordingly, if the quantity of power having-been stored in the battery is large and the quantity of the regenerative power supplied per unit time exceeds the power absorption limit of the battery per unit time, the battery cannot completely absorb the regenerative power as indicated by the graph xe2x80x9caxe2x80x9d in FIG. 7. The excess power is consumed through the heat generation at the battery and during the electrolytic process- of the battery fluid.
As described above, if the quantity of regenerative power supplied per unit time exceeds the power absorption limit of the battery per unit time, all the regenerative power cannot be absorbed by the battery. This poses a problem in that the battery fluid becomes electrolyzed due to the overcharging of the battery and the battery service life is reduced.
Japanese Laid-Open Patent Publication No. H 6-6908 discloses a vehicle battery charge control apparatus that addresses this problem.
The vehicle battery charge control apparatus disclosed in the publication caused the quantity of power charged into the battery to be varied in correspondence to the length of time having elapsed since the battery charge start. Namely, the smaller the length of time having elapsed since the battery charge start, the larger the quantity of power charged into the battery. As a result, the quantity of power is gradually reduced as the charging time lengthens. The correlation between the power absorption limit of the battery per unit time and the length of time over which regenerative power is absorbed into the battery is ascertained in advance through testing. Accordingly, the length of time having elapsed since the charge start is detected and the quantity of power to be charged into the battery is controlled in conformance to the correlation between the detected length of time and the power absorption limit per unit time to prevent the battery from becoming overcharged.
However, since control is implemented in the method disclosed in Japanese Laid-Open Patent Publication No. H 6-6908 so as to simply reduce the quantity of power to be charged into the battery as the battery charge period lengthens, it takes a long time to fully charge the battery, resulting in poor charging efficiency.
An object of the present invention is to provide a charge control apparatus and a charge control method for a vehicle battery that makes it possible to charge the battery with a high degree of efficiency without reducing the battery service life.
The present invention is applied to a charge control apparatus for a vehicle battery comprising a generator that generates power by converting regenerative energy manifesting when the vehicle decelerates to power, a control device that controls battery charge/discharge, a deceleration standby state detection device that detects a deceleration standby state of the vehicle and a decelerating state detection device that detects a decelerating state of the vehicle. In order to achieve the above noted object, the control device implements control so as to start a discharge at the battery if the deceleration standby state detection device detects that the vehicle is in a deceleration standby state and implements control so as to start a battery charge by halting the battery discharge and storing the power generated by the generator if the decelerating state detection device detects that the vehicle is in a decelerating state following the discharge start.
In the charge control method according to the present invention which is adopted in conjunction with a vehicle battery comprising detecting as to whether or not the vehicle is in a deceleration standby state, starting a battery discharge if the vehicle is detected to be in the deceleration standby state, detecting as to whether or not the vehicle is in a deceleration state and starting a battery charge by halting the battery discharge and utilizing regenerative power if the vehicle is detected to be in a decelerating state following the start of the battery discharge.
The present invention is also applies to a charge control apparatus for a vehicle battery comprising a generator that generates power by converting regenerative energy manifesting when the vehicle is decelerating to power, a control device that controls battery charge/discharge, an acceleration detection device that detects the acceleration of the vehicle and a timer that measures the length of discharge time having elapsed since a battery discharge start. In order to achieve the above noted object, the control device implements control so as to start a battery discharge if the acceleration detection device detects that the acceleration of the vehicle has been reduced to a value equal to or lower than 0 and implements control so as to start a battery charge by halting the battery discharge and storing the power generated by the generator when the discharge time measured by the timer matches a predetermined length of time.
In the charge control method according to the present invention which is adopted in conjunction with a vehicle battery comprising detecting the acceleration of the vehicle, starting a battery discharge if the detected acceleration is determined to have become equal to or less than 0 and starting a battery charge by halting the battery discharge and using regenerative power when the length of time having elapsed since the battery discharge start matches a predetermined length of time.